Pregnant sheep will continue to be used for these studies, as they are readily available, are relatively inexpensive (as compared with primates), the fetuses are large enough so that adequate amounts of the several tissues can be studied (cerebral and pulmonary arteries, pituitary and adrenal gland, et cetera), and we and others have amassed a considerable body of physiologic data on this species. Essentially all of the individual projects in this proposal will use pregnant or nonpregnant sheep which have been acclimatized to high altitude, long-term hypoxemia, or normoxic controls. At the time of sacrifice, tissues from these animals will be partitioned among the several investigators and projects. Thus, this Technical Core includes the sheep for these studies. In addition, it includes the expense for several major items of equipment required for most of these experiments. The experimental animal and equipment technical core will be utilized for essentially every project in common by all members of the Center. Such a technical core optimizes the efficient operation of the laboratories, the experiments per se, and the data acquisition and analysis.